Art of cracking hydrocarbons



Nov. 18, 1930. H. K. ROGERS ART OF CRACKING HYDROCARBONS Filed oct. '11; 1928 INVENT /8 BY mf ATToRNi-:Ys

Patented Nov. 18, 1930 unirse lerares einen orricn HORACE K. :ROGERSAOF CHICAGO, YIlLlZILl'@IS, ASSIGNOR T0 SINCLMB REFINING COE- PANY, 0F NEW YORK, N, Y., CORPORATON GF MNE c ABT @F GRACLKING TK YICIRCARBNS Application :tiled October 11,1928. Serial No. 3113,44.

rIhis invention relates to improvements in cracking operations carriedout to produce lower boiling hydrocarbon oils, such as gasoline, from higher boiling hydrocarbon oils, such as kerosene, gas oil and the like; more particularly the invention relates to improvements with respect to the recovery ot lower boilingl hydrocarbon oils, such as gasoline', from gas mixtures produced in such cracking operations.

The usual cracking operations involve the' production not only of the desiredV lovv boiling hydrocarbon oils but also of gases incondensable except under high pressures and at low temperatures. As a consequence, when the desired product is condensed from the gas-vapor mixture from the cracking operation, constituents of the mixture suitable as components of the desired product are carried off uncondensed with the incondensable gases., This invention provides an improved method of recovering such low boiling constituents from such gas mixtures. In the manufacture of gasoline, it has been common practice for some time to subject the raw gas-vapor mixture from the cracking operation to a :Eractionating operation to produce 'directly a gasoline product of the desired boiling range, separating in the ractionating operation all constituents higher boiling than suitable as components ot this gasoline productl rl`his invention 's of special value and application in connection with such operations, but it is also useful in connection with cracking operations which do not include such fractionating operations.

According to the present invention, low boiling but condensable constituents are separated 'from the gas mixtures produced in cracking operations by absorption in an absorbent rnenstruurn and these absorbed constituents are vapor-ized from the absorbent menstruurn, to be condensed and recovered,

, byY heat supplied at least in part from the cracking operation but, instead ot bringing the absorbent menstruuin into direct contact with the gas-vapor mixture from the cracking operation as in some previous practices, this beat exchange to eect this vaporization is carried out indirectly and Without direct contact between the gas-vapor mixture from the cracking operation and the absorbent ,uu-instruuru.l A number of advantages are thus secured. The burden ot stripping higher boiling components of the desired product from the absorbent menstruum absorbed therein during that part of the operation intended to eect vaporization of absorbed constituents rather than `further absorption, for example, is avoided. Where the heat to effect the vaporization ci absorbed constituents from the absorbent menstruum is supplied from the cracking-operation,- this feature of the invention represents an important improvement in making the heat supplied to the cracking operation more usefully available in the cracking operation proper.l Also, accordin to this invention, this heat exchange is eilected at a point from which heat'isrnot usually usefully returned to the cracking operation proper but from Which it is usually rejected, 'orexample t0 Water as a condensing agent. The invention is of special value and application in connection With cracking operations in which the gas- Vapor mixture from the cracking operation is subjected to a iractionating operation to produce directly a product of the desired boiling' range because, for one reason, the stripping burden'j ust mentioned is materially increased in such operations.

The invention `will be further described in connection vvith the accompanying drawings, which illustrate, diagrammatically and conventionally, one Jforni oft' apparatus adapted :for carrying out the process of the invention. lt, is intended and "will be understood that this moredetailed description and illustration are by Way of exemplication; did'erent types of apparatus may be'used to carryy out the Vvarious steps carried out in the apparatus illustrated, the process ci the invention is useful in connection with types of cracking operations other than that carried out in the particular cracking apparatus illustrated, and the process ot the invention may be used 'in connection 'with one or several cracking units.

The cracking still illustrated is yci the generai type described and illustrated in lUnited November 19, 1918, to the Sinclair States Letters Patent No. 1,285,200, granted Aoi. the circulating pump. Residual oil or tar is discharged through. connections 2. A number or' similar cracking stills may be similarly connected to connection 1 through the branch connection shown. For the production of gasoline or gasoline character distillates from gas oil or gas oil character raw stocks, stills of this type are operated under pressures up to 90 to 125 pounds per square inch or somewhat more and with lighter charging stocks, such as kerosene character stocks, higher pressures up to 300 pounds per square inch or more are used.l

The invention is also useful in connection with other types of cracking operations carried out in other types of cracking apparatus, such as those in which the oil to be cracked is heated to a cracking .temperature in the vapor phase at either approximately atmospheric pressure or at higher pressures and processes in which the oil is heated to ajcracking temperature, usually under very high pressures, without complete separation of vapors and unvaporized liquids in the cracking operation itself. The vapors and gases from operation, whether carried out in a cracking still of the type illustrated or in other apparatus, are introduced at an. intermediate point into the fractionating tower 3 through the cracking connection 1. This fractionating tower mayV be of conventional bubblels tower construction or of other construction. adapted to provide close fractionation. By introducing the gas-vapor mixture at an intermediate point, opportunity is provided for the stripping of all low boiling components from the condensate produced in the tower, and any associated oil com onents, below the point of introduction of t e gas-vapor mixture. A heating medium, steam for example, may also be introduced into the lower endv of the tower through connection to promote this stripping action or to assist in control of the` tower. The fractionating operation proper may be controlled by introducing into the upper enel of the tower, throughconnection 5, a suitable reduxing medium such, as a part of the distillate product or a fraction of corresponding character. The condensate pro- Refiningduced in the tower, and any associated oil j components, are discharged through cooler 6 and connection 7. The gases and vapors remaining uncondensed escape through connections 8 and 9. This'fractionating tower 70 may be omitted and the gas-vapor mixture from the cracking operation supplied directly to connection 9, but, as previously mentioned, the invention is of special value and application in connection with operations including a tractionating operation such as is carried out in tower 3.

From connection 9, the gas-vapor mixture, includingthe vapors of the desired product,

passes successively through the heat exchanger 10 and the condenser 11. This heat exchanger may be of any conventional construction. ln carrying out the invention, a part of the vapors maybe condensedl from the gas-vapor mixture in this heat exchanger. 35

nection 13 and the remaining gas-vapormix- 90 ture escapes through connection 1st to the lower end of the scrubbing tower 15.

In the apparatus illustrated, the pressure on the still system may be regulated and reduced by valves between the still and the condenser, for example by valves 16, 17 or 18, or by valves beyond the condenser. Where the condensation is carried out under pressure and the condensate is initially collected under pressure, it is sometimes advantageous to 1Go discharge the condensate into another receiver in which the pressure is reduced and from which any liberated gases and vapors are conducted together with the gas and vapor mixture remaining nncondensed under pressure 10:, to the scrubbing' treatment. 'ln carrylng out the invention in connection with pressure distillation operations, a part of the still pressure may be employed to `torce the gasvapor mixture through'the scrubbing tower. 110

The pressure, for example, may be reduced at a point either between the pressure still and` the condenser or beyond the condenser to a point'suiiiciently above atmospheric pressure to edect this end. The circulation of the gasi vapor mixture through the scrubbing tower may also be effected by a blower, such as isV indicated at 19, or the gas-vapor mixture may be drawn through the` scrubbing tower by means of an exhauster, such as is indicated 12o The `scrubbing tower 15 may be of any conventional construction, for example it may be a tower of conventional construction, fitted interiorly with suitable means to promote distribution and .contacting of the gas-vapor. mixture and the absorbent men.- struum.' Other refinery' gas mixtures, including similar absorbable constituents, coke still tail gases for example, 'may be supplied 139 1,7e1,es4

to the scrubbing tower 15 through connection 21.

An absorbent menstruum is supplied to the scrubbing tower 15 through connection 22. The absorbent menstruum containing constituents absorbed from the gas-vapor mixture supplied to the scrubbing tower is passed, by means of connections 23 and 24 and pump 25, to the heat exchanger 10, in indirect heat exchanging relation with the vapors supplied through connection 9, and then introduced at an intermediate point into the stripping tower 26 through connection 27. This stripping tower may be of conventional bubble tower construction. By 'introducing the charged absorbent menstruum at an intermediate point, opportunity is provided for the stripping of all absorbed low boiling components from the absqrbent menstruum below the point of introduction. The stripped absorbent menstruum is discharged through cooler 28 and connection 29 again to be supplied to the scrubbing tower through connection 22. A heating medium, steam for example, rnay also be introducedinto the lower end of the tower through connection 30 to promote this stripping action or to assist in control of the tower. A cooling medium may also be circulated through the upper end of the tower, through the cooling coil 31 for example, to assist in control of the tower. The constituents absorbed in the scrubbing tower 15 and vaporized from the absorbent menstruum in thestripping tower 26 escape from the upper end of the stripping tower through l connection 32. The gas mixture stripped of constituents absorbed in the scrubbing tower is discharged through connection 33. The vapors escaping through connection .v 32 may be subjected to condensation with the vapors forming the desired product or they may be condensed separately.' In the apparatus illustrated. these vapors may be passed throughk the heat exchanger 10 to the condenser lletogether with the vapors supplied through connection 8, or a separate condenser 34 and receiver 35 may be provided and these vapors may be passed through this condenser. If a sepa-rate condenser 35 is used, any gases and vapors remaining uncondensed may be returned through connection 36 to the scrubbing tower 15. The use o'f a common condenser, however, has several advantages. The lower boiling constituents separated from the gas mixture in the scrubbing treatment are' more easily recovered as a condensate when. condensed with higher boiling components of a composite condensate. Where a common condenser is used, however,

the vapors from the stripping operation must be supplied through connection 32 under a pressure equailing that ot the vapor supplied through connection 8. If the pressure in they ractionating tower 3 exceeds the The apparatus is simplified.`

pressure in the strippin tower 26, a blower 37 may be provided to e ect this purpose.

In carrying out the f invention in the apparatus illustrated, the gas-vapor mixture from the cracking operation proper is rst subjected to a fractionating operation to condense therefrom all constituents higher boiling than suitable as components of the desired product in the ractionating tower 3 and the desired product is then condensed 'from the remaining gas-vapor mixture in the heat exchanger 10 and the condenser 11, the gases and vapors remaining uncondensed are subjected to scrubbing treatment with an absorbent menstruum in the scrubbing tower 15, the absorbent menstruum containing the constituents absorbed in the scrubbing tower 15 is heated by heat exhange with the gasvapor mixture from the cracking operation in the heat exchanger 10, and the absorbed `constituents are vaporized from the thus heated absorbent nienstruum in the stripping tower 26 to be condensed, either in the heat exchanger 10 and thecondenser 11 or in the condenser 34. The stripped absorbent menstruum is returned from the stripping tower 26 to the scrubbing tower 15 so that it is cyclically circulated in the process. An ex- .f

traneous .absorbent menstruum may be used, or, and this is usually the more advantageous practice, some 'oil traction produced 1n or supplied to the operation, higher boiling than the desired product, may be used asthe ab-A sorbent menstruum. For example, mineral seal oil or licht straw oil may be used as an extraneous absorbent nienstruum, or a kerosene character stock or a gas oil character stock, such as is supplied to the cracking operation, or a high boiling traction produced in the operation,` such as the condensate discharged from -a tractionating operation preceding condensation of the desired prodw uct, may be used as an absorbent menstruum. wWhere the condensate produced in the fractionating tower 3, for example, or a similar fraction, is used as the absorbent menstruum, any ldeficiency of the absorbent menstruum may be made up or any excess of the absorbent menstruum may be Idischarged through the cross connection 33 between connections 7 and 29. The ractionating operation carried out in the tower 3 may be controlled, for

example., by `the regulated introduction, through connection 5, of a part of the coinposite cracked product (connection 39 or 40) or a part of the primary lcondensate alone (connection 40) or a part ot the recovered condensates (connection 411) or a similar or suitable traction may be suppiied Jfrom some other source (connection 42). The condon sate produced in the. ra-ctionating tower 3 may be returned to the cracking operation with the raw stock supplied to the cracking operation.

'n carrying out the invention to produce gasoline in the apparatus illustrated, for example, the gas-vapor mixture from the cracking operation proper may be supplied to the fractionating tower through connection 1 at a temperature approximating 500510 F., the gas vapor mixture may escape from the fractionating tower through connection 8 at a temperature approximating 350-360 F., a temperature approximating 295-325o F. may be maintained 1n the lower end of the stripping tower, the vapors may escape from the stripping tower through connection 32 at a temperature approximating 250-260". F., the charged absorbent menstruum :from the scrubbing tower may be heated to a temperature approximating 300-320" lil". in the heat exchanger 10, and steam (dry saturated at 150 pounds per square inch) may be supplied through connection t at a rate approximating 1.1-1.2 pounds per gallon of stripped absorbent menstruum removed with bottom product from the fractionating tower and through connection 30 at a rate approximating 0.1-0.2 pounds per gallon of stripped absorbent menstruum `from the'stripping tower. It will. be understood that these details are intendedl simply to illustrate one operation embodying the invention.

The invention may advantageously be carried out in conjunction with. cracking operations in which a residual oil. product is discharged from a pressure distillation operation and expanded at a lower pressure for the separation from tarry' or cabonaceous` com- `ponents of the residue of Vaporizable oil constituents. In this respect the operation may be carried out, for example, as described in United States Letters Patent No. 1,677 ,77 3, granted July 17, 1928, to the Sinclair Relining Company on the application of Eugene C. Herthel & Thomas de C. Tidt. In such a combined operation, the condensed overhead produc-t from the expander tower may be supplied to the ractionating tower (the tower 3 in the apparatus illustrated), alone or in conjunction with a part of the condensate produced in condenser 11 or condenser 34, for example, as a control medium,

through connections 42 and 5. Such a combined operation may be carried out to pro.- duce from gas oil, for example, gasoline, stripped gas and-a heavy fuel oil residue, the latter from the'expander operation.

The invention may also be carried out in coniunction with a secondary scrubbing treatment of the gas mixture discharged through connection 33 in the apparatus illustrated, for example, as described in United State Letters Patent No. 1,663,868, issued March 27, 1928, to the Sinclair Refining Company on the application of George H. Taber, J r. In such a combined operation, the recovery operation`o the present invention v may be substituted for the independent re.-

connected toconnection 1 through a headerl connection 43.

I claim:

1. In cracking operationsy for the produci tion of lower boiling hydrocarbon oils from higher boiling hydrocarbon oils, the improvement which comprises taking-off a gasvapor mixture from the cracking operation including vapors of the desired product, condensing the desired product therefrom, subjecting the gases and vapors remaining uncondensed to scrubbing treatment with an .absorbent menstruum to absorb thereincondensable constituents of thev gases and vapors, passing the. absorbent menstruum containing absorbed constituents from the scrubbing treatment in indirect heat exchanging relation with the gas-vapor mixture from which the desired product is condensed, vaporlzing absorbed constituents from the thus heated absorbent menstruum while prevent ing direct contact between thelgas-vapor mixture from the racking'operation and the absorbent menstruum and condensing these vaporized constituents.

2. In cracking operations for the production of lower boiling hydrocarbon oils from higher boiling hydrocarbon oils, the improvement which comprises taking of a gas-vapor mixture from the cracking operation including vapors of the desired roduct, condensing the desired product there rom, subjecting the gases and vapors remaining uncondensed to scrubbing treatment with an absorbent menstruum to absorb therein condensable constituents of the gases and vapors. passing the absorbent .menstruum containing absorbed constituents from the scrubbing treatment in indirect heat exchanging relation with the gas-vapor mixture from which the desired product is condensed, vaporizing absorbed constituents from the thus heated absorbent menstruum while -preventing direct contact between the gas-vapor mixture from the cracking operation and the absorbent menstruum `and subjecting these vaporized con` stituents to condensation with the gas-vapor mixture from which the desired product is condensed.

3. In cracking operations for the productionof lower boiling hydrocarbon oils vfrom higher boiling hydrocarbon oils, the improvement which comprises taking off a gas-vapor' mixture from the cracking operation includimg vapors of the desired product and sub- ]ectmg it to a fractionating operation to conlos dense therefrom all constituents higher boilstruum, condensing these vaporized constituing than suitable as components of the deents, and returning the absorbent menstruum sired product, condensing the desired prodto the scrubbing treatment.

uct therefrom, subjecting the gases and vapors remaining uncondensed to' scrubbing treatment with an absorbent menstruum to f absorb therein condensable constituents of the gases and. vapors, passing the absorbent menstruum containing absorbed constituents from the scrubbing treatment in indirectl heat exchanging relation with the gasvapor mixture from which the desired product is condensed, vaporizing absorbed constituents from the thus heated absorbent menstruum while preventingdirect contact between the gas-vapor mixture from the cracking operation and the absorbent menstruum and condensing these vaporized constituents.

4. In cracking operati-ons for the production of lower boiling hydrocarbon oils from higher boiling hydrocarbon oils, the improvement which comprises taking oft' a gasvaoor mixture from the crackmg o eration from the scrubbing treatment in indirect heat exchanging relation with the gas-vapor mixture from which the desired product is condensed, vaporizing absorbed constituents from thethus heated absorbent menstruum while preventing direct ,contact between the gas-vapor mixture from the cracking operation and the absorbent menstruum and subjecting these vaporized constituents to condensation with the gas-vapor mixture from which the desired product is condensed.

5. In cracking operations for the production of lowerboiling hydrocarbon oils Afrom higher boilinghydrocarbon oils, the improvement which comprises taking olf a gas-vapor mixture from the cracking operation including vapors of the desired roduct, condensing the desired product there rom, subjecting the gases and vapors remaining uncondensed t0 scrubbing treatment withian absorbent men- Astruum to absorb ltherein condensable const ituents of the gases and vapors, passing the absorbent .menstruum containing absorbed constituents from the scrubbing treatment in indirectA heat exchanging relation with the gas-vapor mixture from which the desired rproduct is condensed, vaporizing absorbed constituents from the thus heated absorbent menstruum while preventing direct contact between the gas-vapor mixture from the cracking operation and the absorbent men' In `testimony whereof I aiix my si ature.

` HORACE K. RO ERS. 7 0' 

